Proxy-call session control function (p-cscf) to p-cscf communication

ABSTRACT

Apparatuses and methods for P-CSCF to P-CSCF communication are disclosed. In one embodiment, a method implemented in a first proxy-call session control function (P-CSCF) node includes receiving, via a first user plane associated to an Internet Protocol (IP) Multimedia Subsystem (IMS) Protocol Data Unit (PDU) session for a user equipment (UE), a session initiation protocol (SIP) INVITE message; and as a result of the SIP INVITE message and based on a location of the UE relative to a first access gateway (AGW) associated to the first P-CSCF node, determining whether or not to initiate use of at least one of an additional second user plane and an additional second AGW for the IMS PDU session for the UE, the at least one of the second user plane and the second AGW being closer to the UE than the first user plane.

TECHNICAL FIELD

Wireless communication and in particular, methods and apparatuses forP-CSCF to P-CSCF communication.

BACKGROUND

The IP Multimedia Subsystem (hereinafter IMS) enables operators of aPublic Land Mobile Network (hereinafter PLMN) to provide theirsubscribers with multimedia services based and built on Internetapplications, services and protocols. Different services andapplications can be offered on top of IMS. In particular, User Plane(UP) optimization studies for IMS sessions are ongoing in the ThirdGeneration Partnership Project (3GPP). For example, several solutionshave been published in, for example, 3GPP Technical Report (TR) 23.790.However, existing solutions are lacking.

SUMMARY

Some embodiments advantageously provide methods and apparatuses for UPoptimization for IMS sessions. In one aspect, some embodiments addresshow to handle a user equipment (UE) location change and, in particular,some embodiments provide arrangements for changing the access gateway(AGW) associated with a P-CSCF mid-session as a result of a UE locationchange.

In one embodiment, a method implemented in a first proxy-call sessioncontrol function (P-CSCF) node includes receiving, via a first userplane associated to an Internet Protocol (IP) Multimedia Subsystem (IMS)Protocol Data Unit (PDU) session for a user equipment (UE), a sessioninitiation protocol (SIP) INVITE message; and as a result of the SIPINVITE message and/or based on a location of the UE relative to a firstaccess gateway (AGW) associated to the first P-CSCF node, determiningwhether or not to initiate use of an additional second user plane and/oran additional second AGW for the IMS PDU session for the UE, the seconduser plane and/or the second AGW being closer to the UE than the firstuser plane.

In another embodiment, a method implemented in an access and mobilitymanagement (AMF) node includes receiving a subscription request, from aP-CSCF node, to be notified when a location of a user equipment (UE)associated with an IMS PDU session is outside of a coverage area of afirst access gateway (AGW), the subscription request including at leastone of geographic coordinates indicating the coverage area of the firstAGW and geographic coordinates indicating the location of the UE.

In yet another embodiment, a method implemented in a first P-CSCF nodeincludes receiving a request from a second P-CSCF node to reserve atleast one Internet Protocol (IP) address in an access gateway (AGW)controlled by the first P-CSCF node for a user plane and a localapplication server (AS) associated with an IMS PDU session for a userequipment (UE); and/or sending, to the second P-CSCF node, the at leastone IP address reserved in the second AGW for the user plane and thelocal AS to use.

According to one aspect of the present disclosure, a method implementedin a first proxy-call session control function (P-CSCF) node isprovided. The method includes receiving, via a first user planeassociated to an Internet Protocol (IP) Multimedia Subsystem (IMS)Protocol Data Unit (PDU) session for a user equipment (UE), a sessioninitiation protocol (SIP) INVITE message; and as a result of the SIPINVITE message and based on a location of the UE relative to a firstaccess gateway (AGW) associated to the first P-CSCF node, determiningwhether or not to initiate use of at least one of an additional seconduser plane and an additional second AGW for the IMS PDU session for theUE, the at least one of the second user plane and the second AGW beingcloser to the UE than the first user plane.

In some embodiments of this aspect, determining whether or not toinitiate the use of the at least one of the additional second user planeand the additional second AGW for the IMS PDU session further comprisesdetermining, based on session information of the IMS PDU session,whether or not to initiate use of a local application server (AS) forthe IMS PDU session for the UE. In some embodiments of this aspect,determining whether or not to initiate the use of the at least one ofthe additional second user plane and the additional second AGW for theIMS PDU session further comprises determining based at least in part ona media type indicated in the session information. In some embodimentsof this aspect, the method further includes subscribing to an access andmobility management function (AMF) to be notified when a location of theUE is outside of a coverage area of the first AGW, the subscribingincluding at least one of geographic coordinates indicating the coveragearea of the first AGW and geographic coordinates indicating the locationof the UE.

In some embodiments of this aspect, the method further includes, as aresult of the subscribing, receiving a notification that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the received notification;and/or responsive to the received notification, selecting the additionalsecond AGW that has a coverage area corresponding to the indicatedlocation of the UE and/or identifying a second P-CSCF node that controlsthe second AGW. In some embodiments of this aspect, identifying theadditional second AGW further includes using a table indicating aplurality of AGWs, coverage areas associated with each of the pluralityof AGWs and, for each of the plurality of AGWs, an identifier of aP-CSCF node controlling the corresponding one or more AGWs.

In some embodiments of this aspect, the method further includescommunicating with the second P-CSCF node, via a P-CSCF-to-P-CSCFinterface, to initiate a context transfer to the second P-CSCF node. Insome embodiments of this aspect, communicating with the second P-CSCFnode, via a P-CSCF-to-P-CSCF interface, further comprises at least oneof: requesting that the second P-CSCF node reserve at least one InternetProtocol (IP) address in the second AGW for the second user plane andthe local AS; providing, to the second P-CSCF node, addresses associatedwith the second user plane and the local AS to allow the second P-CSCFnode to set-up the second AGW for the second user plane and the local ASfor the IMS PDU session for the UE; receiving, from the second P-CSCFnode, the addresses reserved in the second AGW for the second user planeand the local AS to use; and subscribing to the AMF to be notified whenthe location of the UE is outside of a coverage area of the second AGW.

According to another aspect of the present disclosure, a firstproxy-call session control function (P-CSCF) node is provided. The firstP-CSCF node includes processing circuitry. The processing circuitry isconfigured to cause the first P-CSCF node to receive, via a first userplane associated to an IMS PDU session for a user equipment (UE), asession initiation protocol (SIP) INVITE message; and as a result of theSIP INVITE message and based on a location of the UE relative to a firstaccess gateway (AGW) associated to the first P-CSCF node, determinewhether or not to initiate use of at least one of an additional seconduser plane and an additional second AGW for the IMS PDU session for theUE, the at least one of the second user plane and the second AGW beingcloser to the UE than the first user plane.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to determine whether or not toinitiate the use of the at least one of the additional second user planeand the additional second AGW for the IMS PDU session by beingconfigured to cause the first P-CSCF node to determine, based on sessioninformation of the IMS PDU session, whether or not to initiate use of alocal application server (AS) for the IMS PDU session for the UE. Insome embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to determine whether or not toinitiate the use of the at least one of the additional second user planeand the additional second AGW for the IMS PDU session by beingconfigured to cause the first P-CSCF node to determine based at least inpart on a media type indicated in the session information.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to subscribe to an access andmobility management function (AMF) to be notified when a location of theUE is outside of a coverage area of the first AGW, the subscriptionrequest including at least one of geographic coordinates indicating thecoverage area of the first AGW and geographic coordinates indicating thelocation of the UE. In some embodiments of this aspect, the processingcircuitry is further configured to cause the first P-CSCF node to, as aresult of the subscription, receive a notification that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the received notification;and responsive to the received notification, select the additionalsecond AGW that has a coverage area corresponding to the indicatedlocation of the UE and/or identify a second P-CSCF node that controlsthe second AGW.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to identify the additionalsecond AGW by being configured to cause the first P-CSCF node to use atable indicating a plurality of AGWs, coverage areas associated witheach of the plurality of AGWs and, for each of the plurality of AGWs, anidentifier of a P-CSCF node controlling the corresponding one or moreAGWs. In some embodiments of this aspect, the processing circuitry isfurther configured to cause the first P-CSCF node to communicate withthe second P-CSCF node, via a P-CSCF-to-P-CSCF interface, to initiate acontext transfer to the second P-CSCF node.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to communicate with the secondP-CSCF node, via a P-CSCF-to-P-CSCF interface, by being configured tocause the first P-CSCF node to at least one of request that the secondP-CSCF node reserve at least one Internet Protocol (IP) address in thesecond AGW for the second user plane and the local AS; provide, to thesecond P-CSCF node, addresses associated with the second user plane andthe local AS to allow the second P-CSCF node to set-up the second AGWfor the second user plane and the local AS for the IMS PDU session forthe UE; receive, from the second P-CSCF node, the addresses reserved inthe second AGW for the second user plane and the local AS to use; andsubscribe to the AMF to be notified when the location of the UE isoutside of a coverage area of the second AGW.

According to yet another aspect of the present disclosure, a methodimplemented in an access and mobility management (AMF) node is provided.The method includes receiving a subscription request, from a P-CSCFnode, to be notified when a location of a user equipment (UE) associatedwith an IMS PDU session is outside of a coverage area of a first accessgateway (AGW), the subscription request including at least one ofgeographic coordinates indicating the coverage area of the first AGW andgeographic coordinates indicating the location of the UE.

In some embodiments of this aspect, the method further includesmonitoring the location of the UE relative to the coverage area of thefirst AGW; and if the location of the UE moves outside of the coveragearea of the first AGW, notifying the P-CSCF node that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the notification.

According to another aspect of the present disclosure, an access andmobility management (AMF) node is provided. The AMF node includesprocessing circuitry. The processing circuitry is configured to causethe AMF node to receive a subscription request, from a P-CSCF node, tobe notified when a location of a user equipment (UE) associated with anIMS PDU session is outside of a coverage area of a first access gateway(AGW), the subscription request including at least one of geographiccoordinates indicating the coverage area of the first AGW and geographiccoordinates indicating the location of the UE.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the AMF node monitor the location of the UE relativeto the coverage area of the first AGW; and if the location of the UEmoves outside of the coverage area of the first AGW, notify the P-CSCFnode that the location of the UE is outside of the coverage area of thefirst AGW, the location of the UE indicated in geographic coordinates inthe notification.

According to yet another aspect of the present disclosure, a methodimplemented in a first proxy-call session control function (P-CSCF) nodeis provided. The method includes receiving a request from a secondP-CSCF node to reserve at least one Internet Protocol (IP) address in anaccess gateway (AGW) controlled by the first P-CSCF node for a userplane and a local application server (AS) associated with an IMS PDUsession for a user equipment (UE); and sending, to the second P-CSCFnode, the at least one IP address reserved in the second AGW for theuser plane and the local AS to use.

In some embodiments of this aspect, at least one of: the receiving andsending is via a P-CSCF-to-P-CSCF interface; and receiving includesreceiving, from the second P-CSCF node, addresses associated with theuser plane and the local AS to allow the first P-CSCF node to set-up theAGW for the user plane for the IMS PDU session for the UE. In someembodiments of this aspect, the method further includes reserving therequested addresses in the AGW for the user plane and the local AS touse.

According to another aspect of the present disclosure, a firstproxy-call session control function (P-CSCF) node is provided. The firstP-CSCF node includes processing circuitry. The processing circuitry isconfigured to cause the first P-CSCF node to receive a request from asecond P-CSCF node to reserve at least one Internet Protocol (IP)address in an access gateway (AGW) controlled by the first P-CSCF nodefor a user plane and a local application server (AS) associated with anIMS PDU session for a user equipment (UE); and send, to the secondP-CSCF node, the at least one IP address reserved in the second AGW forthe user plane and the local AS to use.

In some embodiments of this aspect, the processing circuitry is furtherconfigured to cause the first P-CSCF node to at least one of: receiveand send via a P-CSCF-to-P-CSCF interface; and receive, from the secondP-CSCF node, addresses associated with the user plane and the local ASto allow the first P-CSCF node to set-up the AGW for the user plane forthe IMS PDU session for the UE. In some embodiments of this aspect, theprocessing circuitry is further configured to cause the first P-CSCFnode to reserve the requested addresses in the AGW for the user planeand the local AS to use.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 illustrates another example system architecture according to someembodiments of the present disclosure;

FIG. 2 illustrates yet another example system architecture and examplehardware arrangements for devices in the system, according to someembodiments of the present disclosure;

FIG. 3 is a flowchart of an example process in a P-CSCF node accordingto some embodiments of the present disclosure;

FIG. 4 is a flowchart of an example process in an AMF node according tosome embodiments of the present disclosure;

FIG. 5 is a flowchart of yet another example process in a P-CSCF nodeaccording to some embodiments of the present disclosure;

FIG. 6 is a call flow diagram illustrating an example process that mayoptimize a user plane (UP) when there is a UE location change accordingto one embodiment of the present disclosure;

FIG. 7 is a continuation of the call flow diagram of FIG. 6 according tosome embodiments of the present disclosure; and

FIG. 8 is a continuation of the call flow diagram of FIG. 7 according tosome embodiments of the present disclosure.

DETAILED DESCRIPTION

In one aspect, some embodiments address how to handle a user equipment(UE) location change and, in particular, some embodiments providearrangements for changing the access gateway (AGW) associated with aP-CSCF mid-session as a result of a UE location change mid-session.

One embodiment may include:

-   -   if the UE moves to a new area outside the area controlled by the        current/primary P-CSCF/AGW(-CSCF), it may be beneficial to use a        new/target access gateway (AGW) which is controlled by another        P-CSCF (secondary P-CSCF); thus, a P-CSCF to P-CSCF        communication may be used for this.    -   the primary P-CSCF where the UE is IMS registered may remain in        the control plane (CP), but that same primary P-CSCF may be        configured to communicate with the secondary P-CSCF that        controls the target AGW. This communication may enable the        primary P-CSCF to fully control the secondary AGW through        requests issued to the secondary P-CSCF. Hence, in some        embodiments, the secondary P-CSCF operates as a surrogate for        the IMS session of the UE. All controls available to the        secondary P-CSCF for the AGW can be requested through e.g., a        new P-CSCF to P-CSCF interface between the two P-CSCFs from the        primary P-CSCF including lawful intercept, etc. This interface        can, in some embodiments, be a container enabling the primary        P-CSCF to control the secondary AGW just as it controls its own        AGW. Hence, the interface may relay the information to the        secondary P-CSCF then to the secondary/target AGW.

Another embodiment may include:

-   -   a P-CSCF that is configured to control multiple AGWs; hence, not        requiring use of a P-CSCF to P-CSCF communication. In this        embodiment, existing interfaces may be used.

For these embodiments, the P-CSCF may store an identity of the used AGWfor an IMS session in its session state. The AGW may also store theidentity of the P-CSCF that controls it. This can enable traceability,debugging, etc.

Before describing in detail exemplary embodiments, it is noted that theembodiments reside primarily in combinations of apparatus components andprocessing steps related to P-CSCF to P-CSCF communication. Accordingly,components have been represented where appropriate by conventionalsymbols in the drawings, showing only those specific details that arepertinent to understanding the embodiments so as not to obscure thedisclosure with details that will be readily apparent to those ofordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top”and “bottom,” and the like, may be used solely to distinguish one entityor element from another entity or element without necessarily requiringor implying any physical or logical relationship or order between suchentities or elements. The terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting of the concepts described herein. As used herein, the singularforms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises,” “comprising,” “includes” and/or“including” when used herein, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

In embodiments described herein, the joining term, “in communicationwith” and the like, may be used to indicate electrical or datacommunication, which may be accomplished by physical contact, induction,electromagnetic radiation, radio signaling, infrared signaling oroptical signaling, for example. One having ordinary skill in the artwill appreciate that multiple components may interoperate andmodifications and variations are possible of achieving the electricaland data communication.

In some embodiments described herein, the term “coupled,” “connected,”and the like, may be used herein to indicate a connection, although notnecessarily directly, and may include wired and/or wireless connections.

In some embodiments, the non-limiting terms wireless device (WD) or auser equipment (UE) are used interchangeably. The UE herein can be anytype of wireless device capable of communicating with a network node oranother UE over radio signals. In some embodiments, the UE may be anautonomous machine configured to communicate via IMS. The UE herein canby any type of communication device capable of communicating withanother UE, an application server, a network node, a server, an IMS NFor other IMS network node, via a wired connection and/or a wirelessconnection. The UE may also be a radio communication device, targetdevice, device to device (D2D) UE, machine type UE or UE capable ofmachine to machine communication (M2M), low-cost and/or low-complexityUE, a sensor equipped with UE, Tablet, mobile terminals, smart phone,laptop embedded equipped (LEE), laptop mounted equipment (LME), USBdongles, Customer Premises Equipment (CPE), an Internet of Things (IoT)device, or a Narrowband IoT (NB-IOT) device etc.

In some embodiments, the term “node” is used herein and can be any kindof network node, such as, a Proxy-Call Session Control Function (P-CSCF)node, a mobility management node (e.g., Mobility Management Entity (MME)and/or Access and Mobility Function (AMF)), a gateway (e.g., accessgateway), a session management node (e.g., session management function(SMF) node), a user plane function (UPF) node or any network node. Insome embodiments, the network node may be, for example, a subscriberdatabase node, a core network node, a Fifth Generation (5G) and/or NewRadio (NR) network node, an Evolved Packet System (EPS) node, anInternet Protocol (IP) Multimedia Subsystem (IMS) node, a NetworkFunction (NF) node, an Serving-CSCF node, an Interrogating-CSCF node, anetwork repository function (NRF) node, a unified data management (UDM)node, a Network Exposure Function (NEF) node, a home subscriber server(HSS) node, a home location register (HLR) node, etc.

In yet other embodiments, the network node may include any of basestation (BS), radio base station, base transceiver station (BTS), basestation controller (BSC), radio network controller (RNC), g Node B(gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio(MSR) radio node such as MSR BS, multi-cell/multicast coordinationentity (MCE), relay node, integrated access and backhaul (IAB), donornode controlling relay, radio access point (AP), transmission points,transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), acore network node (e.g., mobile management entity (MME), self-organizingnetwork (SON) node, a coordinating node, positioning node, MDT node,etc.), an external node (e.g., 3rd party node, a node external to thecurrent network), nodes in distributed antenna system (DAS), a spectrumaccess system (SAS) node, an element management system (EMS), etc. Thenetwork node may also comprise test equipment. The term “radio node”used herein may be used to also denote a wireless device (WD) such as awireless device (WD) or a radio network node.

A node may include physical components, such as processors, allocatedprocessing elements, or other computing hardware, computer memory,communication interfaces, and other supporting computing hardware. Thenode may use dedicated physical components, or the node may be allocateduse of the physical components of another device, such as a computingdevice or resources of a datacenter, in which case the node is said tobe virtualized. A node may be associated with multiple physicalcomponents that may be located either in one location, or may bedistributed across multiple locations.

Signaling may generally comprise one or more symbols and/or signalsand/or messages. A signal may comprise or represent one or more bitsand/or media packets. An indication may represent signaling, and/or beimplemented as a signal, or as a plurality of signals. One or moresignals may be included in and/or represented by a message. Signaling,in particular control signaling, may comprise a plurality of signalsand/or messages, which may be transmitted on different carriers and/orbe associated to different signaling processes, e.g. representing and/orpertaining to one or more such processes and/or correspondinginformation. An indication may comprise signaling, and/or a plurality ofsignals and/or messages and/or may be comprised therein. Signalingassociated to an interface may be transmitted via the interface.

An indication generally may explicitly and/or implicitly indicate theinformation it represents and/or indicates. Implicit indication may forexample be based on position and/or resource used for transmission.Explicit indication may for example be based on a parametrization withone or more parameters, and/or one or more index or indicescorresponding to a table, and/or one or more bit patterns representingthe information.

In some embodiments, a geographic location (e.g., as defined by e.g.,geographic coordinates) may be considered different from a location thatis defined by a cell identifier or tracking area.

In some embodiments, the term “close” and “closer” is used and mayindicate an element or node or associated area (e.g., target AGW, UP,UPF, etc.) that is geographically close or geographically closer toe.g., a UE location as compared to another element or node or associatedarea (e.g., primary/initial AGW, initial UP, initial UPF for an IMS PDUsession associated with the UE).

Any two or more embodiments described in this disclosure may be combinedin any way with each other.

Note also that some embodiments of the present disclosure may besupported by standard documents disclosed in Third GenerationPartnership Project (3GPP) technical specifications. That is, someembodiments of the description can be supported by the above documents.In addition, all the terms disclosed in the present document may bedescribed by the above standard documents.

Note that although terminology from one particular wireless system, suchas, for example, 3^(rd) Generation Partnership Project (3GPP), Long TermEvolution (LTE), 5^(th) Generation (5G) and/or New Radio (NR), may beused in this disclosure, this should not be seen as limiting the scopeof the disclosure to only the aforementioned system. Other wirelesssystems, including without limitation Wide Band Code Division MultipleAccess (WCDMA), Worldwide Interoperability for Microwave Access (WiMax),Ultra Mobile Broadband (UMB) and Global System for Mobile Communications(GSM), may also benefit from exploiting the ideas covered within thisdisclosure.

Note further, that functions described herein as being performed by aP-CSCF node, an AMF node, or any other network node described herein arenot limited to performance by a single physical device and, in fact, canbe distributed among several physical devices.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Referring to the drawing figures, in which like elements are referred toby like reference numerals, there is shown in FIG. 1 a schematic diagramof the communication system 10, according to an embodiment, constructedin accordance with the principles of the present disclosure. Thecommunication system 10 in FIG. 1 is a non-limiting example and otherembodiments of the present disclosure may be implemented by one or moreother systems and/or networks. Referring to FIG. 1, the system 10includes an AMF node 12, an SMF node 14, one or more UPF nodes 16 a and16 b (collectively referred to as UPF node 16). The system 10 mayinclude a first P-CSCF node 18 a and a second P-CSCF node 18 b andassociated access gateway (AGW) nodes 20 a and 20 b, respectively. Insome embodiments, there may be a P-CSCF-to-P-CSCF interface 21 betweenP-CSCF node 18 a and 18 b for communications between P-CSCFs 18according to some embodiments of the present disclosure. In otherembodiments, the system 10 may not include the P-CSCF-to-P-CSCFinterface 21 but the P-CSCF to P-CSCF communications may be implementedusing existing interfaces. In some embodiments, the system 10 may notinclude the P-CSCF-to-P-CSCF direct interface 21, but the P-CSCF toP-CSCF communications may be indirect and performed via existinginterfaces, e.g., through the UPFs, ostensibly using the UPF as arouter.

The system 10 may further include a user equipment (UE) 22 and one ormore radio access networks (RANs) 24. The RAN(s) 24 may include, e.g.,5G RAN also known as NR RAN, which may provide radio access to the UE22. The various nodes may support one or more of the techniquesdisclosed herein for arranging the UP (e.g., UPF node 16, etc.) closerto the UE 22 when a UE 22 changes location mid-session according to someembodiments of the present disclosure. It should be understood that thesystem 10 may include numerous nodes of those shown in FIG. 1, as wellas, additional nodes not shown in FIG. 1. In addition, the system 10 mayinclude many more connections/interfaces than those shown in FIG. 1. Forexample, there may be a connection/interface between the SMF and each ofthe UPFs as the SMF may in some embodiments control both UPFs.

The system 10 may include one or more nodes having a requestor 26, anotifier 28 and/or a reserver 30. The P-CSCF node 18 may include therequestor 26 which may be configured to one or more of: receive, via afirst user plane associated to an IMS PDU session for a user equipment(UE), a session initiation protocol (SIP) INVITE message; and/or as aresult of the SIP INVITE message and/or based on a location of the UErelative to a first access gateway (AGW) associated to the first P-CSCFnode, determine whether or not to initiate use of an additional seconduser plane and/or an additional second AGW for the IMS PDU session forthe UE, the second user plane and/or the second AGW being closer to theUE than the first user plane.

The AMF node 12 may include the notifier 28 which may be configured toreceive a subscription request, from a P-CSCF node, to be notified whena location of a user equipment (UE) associated with an IMS PDU sessionis outside of a coverage area of a first access gateway (AGW), thesubscription request including at least one of geographic coordinatesindicating the coverage area of the first AGW and geographic coordinatesindicating the location of the UE.

In some embodiments, the P-CSCF node 18 may include the reserver 30which may be configured to one or more of receive a request from asecond P-CSCF node to reserve at least one Internet Protocol (IP)address in an access gateway (AGW) controlled by the first P-CSCF nodefor a user plane and a local application server (AS) associated with anIMS PDU session for a user equipment (UE); and/or send, to the secondP-CSCF node, the at least one IP address reserved in the second AGW forthe user plane and the local AS to use.

Example implementations, in accordance with some embodiments, of aP-CSCF node 18, an AMF node 12, and another network node 32, which mayinclude any of the network nodes discussed herein and will now bedescribed with reference to FIG. 2.

The P-CSCF node 18 includes a communication interface 34, processingcircuitry 36, and memory 38. The communication interface 34 may beconfigured to communicate with any of the nodes in the system 10according to some embodiments of the present disclosure. In someembodiments, the communication interface 34 may be formed as or mayinclude, for example, one or more radio frequency (RF) transmitters, oneor more RF receivers, and/or one or more RF transceivers, and/or may beconsidered a radio interface. In some embodiments, the communicationinterface 34 may also include a wired interface.

The processing circuitry 36 may include one or more processors 40 andmemory, such as, the memory 38. In particular, in addition to atraditional processor and memory, the processing circuitry 36 maycomprise integrated circuitry for processing and/or control, e.g., oneor more processors and/or processor cores and/or FPGAs (FieldProgrammable Gate Array) and/or ASICs (Application Specific IntegratedCircuitry) adapted to execute instructions. The processor 40 may beconfigured to access (e.g., write to and/or read from) the memory 38,which may comprise any kind of volatile and/or nonvolatile memory, e.g.,cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM(Read-Only Memory) and/or optical memory and/or EPROM (ErasableProgrammable Read-Only Memory).

Thus, the P-CSCF node 18 may further include software stored internallyin, for example, memory 38, or stored in external memory (e.g.,database) accessible by the P-CSCF node 18 via an external connection.The software may be executable by the processing circuitry 36. Theprocessing circuitry 36 may be configured to control any of the methodsand/or processes described herein and/or to cause such methods, and/orprocesses to be performed, e.g., by the P-CSCF node 18 (e.g., P-CSCFnodes 18 a and/or 18 b, etc.). The memory 38 is configured to storedata, programmatic software code and/or other information describedherein. In some embodiments, the software may include instructionsstored in memory 38 that, when executed by the processor 40 and/orrequestor 26 and/or reserver 30 causes the processing circuitry 36and/or configures the P-CSCF node 18 to perform the processes describedherein with respect to the P-CSCF node 18 (e.g., processes describedwith reference to FIGS. 3 and/or 5 and/or any of the other flowcharts).

The AMF node 12 includes a communication interface 42, processingcircuitry 44, and memory 46. The communication interface 42 may beconfigured to communicate with the UE 22 and/or other elements in thesystem 10 according to some embodiments of the present disclosure. Insome embodiments, the communication interface 42 may be formed as or mayinclude, for example, one or more radio frequency (RF) transmitters, oneor more RF receivers, and/or one or more RF transceivers, and/or may beconsidered a radio interface. In some embodiments, the communicationinterface 42 may also include a wired interface.

The processing circuitry 44 may include one or more processors 48 andmemory, such as, the memory 46. In particular, in addition to atraditional processor and memory, the processing circuitry 44 maycomprise integrated circuitry for processing and/or control, e.g., oneor more processors and/or processor cores and/or FPGAs (FieldProgrammable Gate Array) and/or ASICs (Application Specific IntegratedCircuitry) adapted to execute instructions. The processor 48 may beconfigured to access (e.g., write to and/or read from) the memory 46,which may comprise any kind of volatile and/or nonvolatile memory, e.g.,cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM(Read-Only Memory) and/or optical memory and/or EPROM (ErasableProgrammable Read-Only Memory).

Thus, the AMF node 12 may further include software stored internally in,for example, memory 46, or stored in external memory (e.g., database)accessible by the AMF node 12 via an external connection. The softwaremay be executable by the processing circuitry 44. The processingcircuitry 44 may be configured to control any of the methods and/orprocesses described herein and/or to cause such methods, and/orprocesses to be performed, e.g., by the AMF node 12. The memory 46 isconfigured to store data, programmatic software code and/or otherinformation described herein. In some embodiments, the software mayinclude instructions stored in memory 46 that, when executed by theprocessor 48 and/or notifier 28, causes the processing circuitry 44and/or configures the AMF node 12 to perform the processes describedherein with respect to the AMF node 12 (e.g., processes described withreference to FIG. 4 and/or any of the other flowcharts).

The network node 32 (for ease of understanding and explanation, nodessuch as an AS node, an SMF node, a UPF node, an AGW node, a policycontrol function (PCF) node, etc., are referred to collectively asnetwork node 32) includes a communication interface 50, processingcircuitry 52, and memory 54. The communication interface 50 may beconfigured to communicate with any of the nodes in the system 10according to some embodiments of the present disclosure. In someembodiments, the communication interface 50 may be formed as or mayinclude, for example, one or more radio frequency (RF) transmitters, oneor more RF receivers, and/or one or more RF transceivers, and/or may beconsidered a radio interface. In some embodiments, the communicationinterface 50 may also include a wired interface.

The processing circuitry 52 may include one or more processors 56 andmemory, such as, the memory 54. In particular, in addition to atraditional processor and memory, the processing circuitry 52 maycomprise integrated circuitry for processing and/or control, e.g., oneor more processors and/or processor cores and/or FPGAs (FieldProgrammable Gate Array) and/or ASICs (Application Specific IntegratedCircuitry) adapted to execute instructions. The processor 56 may beconfigured to access (e.g., write to and/or read from) the memory 54,which may comprise any kind of volatile and/or nonvolatile memory, e.g.,cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM(Read-Only Memory) and/or optical memory and/or EPROM (ErasableProgrammable Read-Only Memory).

Thus, the network node 32 may further include software stored internallyin, for example, memory 54, or stored in external memory (e.g.,database) accessible by the network node 32 via an external connection.The software may be executable by the processing circuitry 52. Theprocessing circuitry 52 may be configured to control any of the methodsand/or processes described herein and/or to cause such methods, and/orprocesses to be performed, e.g., by the network node 32 (e.g., an AMFnode, an SMF node, a UPF node, an MME node and/or a gateway node, etc.).The memory 54 is configured to store data, programmatic software codeand/or other information described herein. In some embodiments, thesoftware may include instructions stored in memory 54 that, whenexecuted by the processor 56, causes the processing circuitry 52 and/orconfigures the network node 32 to perform the processes described hereinwith respect to the network node 32 (e.g., an AMF node, an SMF node, aUPF node, an MME node and/or a gateway node, etc.).

In FIG. 2, the connection between the P-CSCF node 18, AMF node 12 andnetwork node 32 is shown without explicit reference to any intermediarydevices or connections. However, it should be understood thatintermediary devices and/or connections may exist between these devices,although not explicitly shown. It is also understood that P-CSCF node18, AMF node 12 and network node 32 may be connected to a cloud networkand in communication with each other over that cloud network. In otherwords, although the P-CSCF node 18, AMF node 12 and network node 32 areshown connected serially, such is not necessarily the case.

Although FIG. 2 shows requestor 26, reserver 30 and notifier 28, asbeing within a respective processor, it is contemplated that theseelements may be implemented such that a portion of the elements isstored in a corresponding memory within the processing circuitry. Inother words, the elements may be implemented in hardware or in acombination of hardware and software within the processing circuitry.

FIG. 3 is a flowchart of an example process in a P-CSCF node 18 fore.g., arranging the UP closer to the UE 22 when the UE 22 changeslocation according to some embodiments of the present disclosure. One ormore Blocks and/or functions and/or methods performed by the P-CSCF node18 may be performed by one or more elements of P-CSCF node 18 such as byrequestor 26 in processing circuitry 36, memory 38, processor 40,communication interface 34, etc. according to the exampleprocess/method. The example process includes receiving (Block S100),such as via requestor 26, processing circuitry 36, memory 38, processor40, and/or communication interface 34, via a first user plane associatedto an Internet Protocol (IP) Multimedia Subsystem (IMS) Protocol DataUnit (PDU) session for a user equipment (UE), a session initiationprotocol (SIP) INVITE message. The method includes e.g., as a result ofthe SIP INVITE message and/or based on a location of the UE relative toa first access gateway (AGW) associated to the first P-CSCF node,determining (Block S102), such as via requestor 26, processing circuitry36, memory 38, processor 40, and/or communication interface 34, whetheror not to initiate use of at least one of an additional second userplane and an additional second AGW for the IMS PDU session for the UE,the at least one of the second user plane and the second AGW beingcloser to the UE than the first user plane.

In some embodiments, determining, such as via requestor 26, processingcircuitry 36, memory 38, processor 40, and/or communication interface34, whether or not to initiate the use of the at least one of theadditional second user plane and the additional second AGW for the IMSPDU session further includes determining, based on session informationof the IMS PDU session, whether or not to initiate use of a localapplication server (AS) for the IMS PDU session for the UE. In someembodiments, determining, such as via requestor 26, processing circuitry36, memory 38, processor 40, and/or communication interface 34, whetheror not to initiate the use of the at least one of the additional seconduser plane and the additional second AGW for the IMS PDU session furtherincludes determining based at least in part on a media type indicated inthe session information.

In some embodiments, the method further includes subscribing, such asvia requestor 26, processing circuitry 36, memory 38, processor 40,and/or communication interface 34, to an access and mobility managementfunction (AMF) to be notified when a location of the UE is outside of acoverage area of the first AGW, the subscribing including at least oneof geographic coordinates indicating the coverage area of the first AGWand geographic coordinates indicating the location of the UE. In someembodiments, the method further includes, as a result of thesubscribing, receiving, such as via requestor 26, processing circuitry36, memory 38, processor 40, and/or communication interface 34, anotification that the location of the UE is outside of the coverage areaof the first AGW, the location of the UE indicated in geographiccoordinates in the received notification. In some embodiments, themethod includes, responsive to the received notification, selecting theadditional second AGW that has a coverage area corresponding to theindicated location of the UE and/or identifying a second P-CSCF nodethat controls the second AGW.

In some embodiments, identifying, such as via requestor 26, processingcircuitry 36, memory 38, processor 40, and/or communication interface34, the additional second AGW further includes using a table indicatinga plurality of AGWs, coverage areas associated with each of theplurality of AGWs and, for each of the plurality of AGWs, an identifierof a P-CSCF node controlling the corresponding one or more AGWs. In someembodiments, the method further includes communicating, such as viarequestor 26, processing circuitry 36, memory 38, processor 40, and/orcommunication interface 34, with the second P-CSCF node, via aP-CSCF-to-P-CSCF interface, to initiate a context transfer to the secondP-CSCF node.

In some embodiments, communicating with the second P-CSCF node, via aP-CSCF-to-P-CSCF interface, further includes one or more of: requestingthat the second P-CSCF node reserve at least one Internet Protocol (IP)address in the second AGW for the second user plane and the local AS;providing, to the second P-CSCF node, addresses associated with thesecond user plane and the local AS to allow the second P-CSCF node toset-up the second AGW for the second user plane and the local AS for theIMS PDU session for the UE; receiving, from the second P-CSCF node, theaddresses reserved in the second AGW for the second user plane and thelocal AS to use; and/or subscribing to the AMF to be notified when thelocation of the UE is outside of a coverage area of the second AGW.

FIG. 4 is a flowchart of an example process in an AMF node 12 for e.g.,notifying the P-CSCF node 18 of a change in the UE location according tosome embodiments of the present disclosure. One or more Blocks and/orfunctions and/or methods performed by the AMF node 12 may be performedby one or more elements of AMF node 12 such as notifier 28 in processingcircuitry 44, memory 46, processor 48, communication interface 42, etc.according to the example process/method. The example process includesreceiving (Block S104), such as via notifier 28, processing circuitry44, memory 46, processor 48, communication interface 42, receiving asubscription request, from a P-CSCF node, to be notified when a locationof a user equipment (UE) associated with an IMS PDU session is outsideof a coverage area of a first access gateway (AGW), the subscriptionrequest including at least one of geographic coordinates indicating thecoverage area of the first AGW and geographic coordinates indicating thelocation of the UE.

In some embodiments, the method further includes monitoring, such as vianotifier 28, processing circuitry 44, memory 46, processor 48,communication interface 42, the location of the UE relative to thecoverage area of the first AGW; and if the location of the UE movesoutside of the coverage area of the first AGW, notifying, such as vianotifier 28, processing circuitry 44, memory 46, processor 48,communication interface 42, the P-CSCF node that the location of the UEis outside of the coverage area of the first AGW, the location of the UEindicated in geographic coordinates in the notification.

FIG. 5 is a flowchart of an example process in a P-CSCF node 18 (e.g.,secondary P-CSCF node 18 b) for e.g., setting up an AGW to support thecloser UP when the UE 22 changes location according to some embodimentsof the present disclosure. One or more Blocks and/or functions and/ormethods performed by the P-CSCF node 18 may be performed by one or moreelements of P-CSCF node 18 such as by reserver 30 in processingcircuitry 36, memory 38, processor 40, communication interface 34, etc.according to the example process/method. The example process includesreceiving (Block S106), such as via reserver 30, processing circuitry36, memory 38, processor 40, and/or communication interface 34, arequest from a second P-CSCF node to reserve at least one InternetProtocol (IP) address in an access gateway (AGW) controlled by the firstP-CSCF node for a user plane and a local application server (AS)associated with an IMS PDU session for a user equipment (UE). The methodincludes sending (Block S108), such as via reserver 30, processingcircuitry 36, memory 38, processor 40, and/or communication interface34, to the second P-CSCF node, the at least one IP address reserved inthe second AGW for the user plane and the local AS to use.

In some embodiments, the receiving and sending is via a P-CSCF-to-P-CSCFinterface. In some embodiments, receiving includes receiving, from thesecond P-CSCF node, addresses associated with the user plane and thelocal AS to allow the first P-CSCF node to set-up the AGW for the userplane for the IMS PDU session for the UE.

In some embodiments, the method includes reserving, such as via reserver30, processing circuitry 36, memory 38, processor 40, and/orcommunication interface 34, the requested addresses in the AGW for theuser plane and the local AS to use.

Having generally described arrangements for e.g., P-CSCF to P-CSCFcommunication that may be used to, e.g., arrange the UP closer to the UE22 when the UE 22 changes location, a more detailed description of someof the embodiments are provided as follows with reference to FIGS. 6-8,and which may be implemented by AMF node 12, P-CSCF node 18 and/or moregenerally the network node 32.

An example embodiment is described with reference to the call flowdepicted in FIG. 6, as well as, FIGS. 7 and 8, which are continuationsof the example call flow.

In step S110, the UE 22 performs a 5G registration (e.g., as defined in3GPP Technical Specification (TS) 23.502, section 4.2.2). In step S112,the UE 22 performs a PDU establishment with an Internet Protocol (IP)Multimedia Subsystem (IMS) DDN (e.g., as defined in TS 23.502, section4.3.2). In step S114, the UE 22 performs IMS registration (e.g., asdefined in TS 23.228). When the IMS PDU session is setup in step S112,the user plane 1 (UP1) (e.g., UPF node 16 a) is allocated by SMF1 14 tothe UE 22 and the IMS SIP signaling now traverses through UP1 (e.g., UPFnode 16 a), as shown by the dashed line in step S116 between the UE 22and SCSCF node 58.

In step S118, the UE 22 initiates a SIP INVITE with AS1 60 to the P-CSCFnode 18 a. In step S120, the P-CSCF node 18 a may determine whether ornot the UP for that IMS PDU session should be close to the UE 22. TheP-CSCF node 18 a may use the negotiated session information to determineif media optimization is desirable (e.g., would optimize the UP). Forexample, if the P-CSCF node 18 a determines that the session is a videostreaming session and the P-CSCF node 18 a can locate an AS close to theUE 22, then media optimization is desirable and may be initiated by theP-CSCF node 18. On the other hand, if, for example, the session is aVoice-over LTE (VOLTE) session, then media optimization may not beapplicable. The P-CSCF node 18 a may select an AGW 20 that is close tothe UE 22 (e.g., closer to the UE 22 than the current AGW 20 for thecurrent UP) for the media.

In steps S122-S128, the P-CSCF node 18 a requests a policy update from aPCF node 62 to modify the PDU session for the UE 22 and to allocate anew UP (e.g., UP2 media/UPF node 16 b) close to the UE 22 for the IMSsession (e.g., closer to the UE 22 than the current UP1/UPF1 node 16 a).The P-CSCF node 18 a may not impact the SIP signaling PDU session whichcontinues to use UP1 (e.g., UP1 SIP/UPF node 16 a).

Referring now to FIG. 7, a continuation of the example call flow isdescribed. In steps S130-S140, the SMF1 node 14 may now allocate a newUP2 (e.g., UPF node 16 b) for the media associated with the UE 22. Thus,the UE 22 may be allocated a new IP address anchored in UP2 (e.g., UPFnode 16 b) associated with the media and which is close to the UE 22location (e.g., closer to the UE 22 than the current UP1 (UPF1 node 16a). The UE 22 may retain the IP address anchored in UP1 (e.g., UPF node16 a) for SIP signaling only (hence, the term SIP shown in FIG. 7beneath UP1). The SMF node 14 may engage a UP classifier (e.g., UPF node16 c) to accomplish this (e.g., to arrange SIP signaling for UP1 andmedia for UP2 to the UE 22). After that SIP traffic flows through UP1,while the media flows the UP2 and the AGW1 (e.g., target AGW node 20).

At least some behavior/communication in steps S130-S140 may be based one.g., 3GPP Technical Specification (TS) 23.502, section 4.3.5.4, whichmay be incorporated herein by reference. To summarize, in step S130, theSMF node 14 inserts a classifier and, in step S132, updates the downlinkand the uplink for the SIP signalling traffic which now goes through theUP classifier (e.g., UPF node 16 c), the UP1 (UPF node 16 a) and the AGWnode 20, to the IMS domain, as shown in step S134.

In step S136, the SMF node 14 allocates UP2 (e.g., UPF node 16 b) forthe IMS session (media part) and configures the UE 22 with a new IPaddress for the IMS session (media part).

In steps S138 and S140, the SMF node 14 updates the uplink and downlinkfor the IMS media which now can be seen in step S142, flowing throughthe UP classifier (e.g., UPF node 16 c), UP2 (e.g., UPF node 16 b) andAGW node 20.

In step S144, the IMS session setup is complete; however, since the UE22 has used an address allocated in UP1, while the media will use UP2,the UE 22 may send, in step S146, a SIP re-INVITE message (e.g., to theprimary P-CSCF node 18 a) to update the new IP address used for thatsession to support use of the new UP2 for media.

In step S148, the P-CSCF node 18 a subscribes to the AMF node 12 (viathe network exposure function (NEF) although not shown) to be notifiedwhen the UE 22 leaves the coverage area of the AGW node 20. In existingnetworks, only cell identifiers (IDs), or tracking area can be specifiedas an area of interest, but in some embodiments of the presentdisclosure, the P-CSCF node 18 a may specify a location of interest(e.g., UE 22 location, AGW coverage area, etc.) based on geographiclocation/coordinates, such as, for example, the Digital cellulartelecommunications system (Phase 2+); Universal Geographical AreaDescription (GAD) (3GPP TS 03.32 version 7.2.0 Release 1998). The P-CSCFnode 18 a and the AMF node 12 may be configured to support thisspecification for specifying a location of interest using geographicalcoordinates.

Referring now to FIG. 8, a continuation of the example call flow isdescribed. In step S150, the P-CSCF node 18 a is notified (e.g., by theAMF node 12) that the UE 22 moved from the area of interest (e.g.,coverage area of primary AGW1 node 20 a associated with primary P-CSCFnode 18 a) and, as a result, the P-CSCF node 18 a may determine toallocate a new/closer AGW2 node 20 b for the UE 22. The notification mayinclude the UE's 22 new geographical coordinates.

In step S152, the P-CSCF node 18 a is configured with the informationthat is used to determine the target AGW2 node 20 b appropriate for thenew area in which the UE 22 is located and/or to determine the secondaryP-CSCF2 (e.g., the P-CSCF node 18 b) controlling that target AGW2 node20 b. In some embodiments, each P-CSCF node 18 will be configured orpre-configured with a table, or the like, that includes all locations ofinterest (e.g., geographic coordinates defining each AGW coverage area),identified as per e.g., the ETSI/3GPP specification mentioned above, forthe public land mobile network (PLMN) that the operator is responsiblefor, the AGW identities that can be used in each (one or more) locationarea, and an identity of the P-CSCF node 18 controlling the respectiveAGW node 20. This can enable the P-CSCF node 18 to use this table inconjunction with the UE 22 location received in the notification inorder to locate the secondary P-CSCF2 (e.g., P-CSCF node 18 b) and/orsecondary/target AGW2 (e.g., AGW2 node 20 b).

In step S154, the primary P-CSCF1 (e.g., P-CSCF node 18 a) communicates(e.g., via interface 21) with the secondary P-CSCF2 (e.g., P-CSCF node18 b) to request the proper addresses to enable the target AGW2 node 20b to be used for media. As stated before, in some embodiments, theprimary P-CSCF1 (e.g., P-CSCF node 18 a) may control the secondary AGW2node 20 b identical to how it controls its own AGW1 node 20 a. Theprimary P-CSCF1 node 18 a may send to the secondary P-CSCF2 node 18 bthe UP2 (e.g., UPF2 node 16 b) and AS1 addresses so that the secondaryP-CSCF2 node 18 b can allocate the proper addresses in the target AGW2node 20 b and allow the media to pass through from the UP2 (e.g., UPF2node 16 b) to AS1 to flow through the target AGW2 node 20 b.

In step S156, the secondary P-CSCF2 18 b may allocate the requiredaddresses in the AGW2 node 20 b to allow the media associated with theIMS PDU session of the UE 22 to flow through AGW2 node 20 b (instead ofthe AGW1 node 20 a). Additionally, in step S156, the secondary P-CSCF218 b, opens the necessary pin holes in the AGW2 node 20 b for the mediato go through.

In step S158, the secondary P-CSCF2 node 18 b may report to the primaryP-CSCF1 node 18 a (e.g., via interface 21) the successful allocation hasoccurred and may report the new addresses in the AGW2 node 20 b for theUP2 and AS1 to use.

In steps S160 and S162, the primary P-CSCF1 node 18 a modifies the PCFauthorization policy to enable the SMF node 14 to modify the session sothat UP2 now uses the AGW2 node 20 b address provided in step S158.

In step S165, the P-CSCF 18 updates the IMS session so that AS1 now alsocommunicates with the AGW2 node 20 b using the address provided in stepS158. Such communication of AS1 with AGW2 node 20 b using the address isshown in the call flow lines indicated by S166.

The new flow of the media is shown in step S166.

In step S168, the primary P-CSCF1 node 18 a then subscribes to the newlocation of interest (e.g., geographic coordinates defining the coveragearea of AGW2 and/or the new UE location) based on the new UE 22 locationreceived in step S150.

In some embodiments, e.g., where one P-CSCF may be associated to morethan one AGW, one or more of the steps discussed above as beingperformed by the secondary P-CSCF may occur internally at the primaryP-CSCF in order to redirect the media traffic to the new AGW that iscloser to the changed UE location.

Some embodiments may include one or more of the following:

Embodiment A1. A method implemented in a first proxy-call sessioncontrol function (P-CSCF) node, the method comprising:

receiving, via a first user plane associated to an Internet Protocol(IP) Multimedia Subsystem (IMS) Protocol Data Unit (PDU) session for auser equipment (UE), a session initiation protocol (SIP) INVITE message;and

as a result of the SIP INVITE message and/or based on a location of theUE relative to a first access gateway (AGW) associated to the firstP-CSCF node, determining whether or not to initiate use of an additionalsecond user plane and/or an additional second AGW for the IMS PDUsession for the UE, the second user plane and/or the second AGW beingcloser to the UE than the first user plane.

Embodiment A2. The method of Embodiment A1, wherein determining whetheror not to initiate the use of the additional second user plane for theIMS PDU session further comprises:

determining, based on session information of the IMS PDU session,whether or not to initiate use of a local application server (AS) forthe IMS PDU session for the UE.

Embodiment A3. The method of Embodiment A2, wherein determining whetheror not to initiate the use of the additional second user plane for theIMS PDU session further comprises determining based at least in part ona media type indicated in the session information.

Embodiment A4. The method of any one of Embodiments A1-A3, furthercomprising:

subscribing to an access and mobility management function (AMF) to benotified when a location of the UE is outside of a coverage area of thefirst AGW, the subscribing including at least one of geographiccoordinates indicating the coverage area of the first AGW and geographiccoordinates indicating the location of the UE.

Embodiment A5. The method of Embodiment A4, further comprising:

as a result of the subscribing, receiving a notification that thelocation of the UE is outside of the coverage area of the first AGW, thelocation of the UE indicated in geographic coordinates in the receivednotification; and/or responsive to the received notification, selectingthe additional second AGW that has a coverage area corresponding to theindicated location of the UE and/or identifying a second P-CSCF nodethat controls the second AGW.

Embodiment A6. The method of Embodiment A5, wherein identifying theadditional second AGW further comprises:

using a table indicating a plurality of AGWs, coverage areas associatedwith each of the plurality of AGWs and, for each of the plurality ofAGWs, an identifier of a P-CSCF node controlling the corresponding oneor more AGWs.

Embodiment A7. The method of any one of Embodiments A5 and A6, furthercomprising:

communicating with the second P-CSCF node, via a P-CSCF-to-P-CSCFinterface, to initiate a context transfer to the second P-CSCF node.

Embodiment A8. The method of Embodiment A7, wherein communicating withthe second P-CSCF node, via a P-CSCF-to-P-CSCF interface, furthercomprises one or more of:

requesting that the second P-CSCF node reserve at least one InternetProtocol (IP) address in the second AGW for the second user plane andthe local AS;

providing, to the second P-CSCF node, addresses associated with thesecond user plane and the local AS to allow the second P-CSCF node toset-up the second AGW for the second user plane and the local AS for theIMS PDU session for the UE;

receiving, from the second P-CSCF node, the addresses reserved in thesecond AGW for the second user plane and the local AS to use; and/orsubscribing to the AMF to be notified when the location of the UE isoutside of a coverage area of the second AGW.

Embodiment B1. A first proxy-call session control function (P-CSCF)node, the first P-CSCF node comprising processing circuitry, theprocessing circuitry configured to cause the first P-CSCF node to:

receive, via a first user plane associated to an IMS PDU session for auser equipment (UE), a session initiation protocol (SIP) INVITE message;and

as a result of the SIP INVITE message and/or based on a location of theUE relative to a first access gateway (AGW) associated to the firstP-CSCF node, determine whether or not to initiate use of an additionalsecond user plane and/or an additional second AGW for the IMS PDUsession for the UE, the second user plane and/or the second AGW beingcloser to the UE than the first user plane.

Embodiment B2. The first P-CSCF node of Embodiment B1, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to determine whether or not to initiate the use of the additionalsecond user plane for the IMS PDU session by being configured to causethe first P-CSCF node to:

determine, based on session information of the IMS PDU session, whetheror not to initiate use of a local application server (AS) for the IMSPDU session for the UE.

Embodiment B3. The first P-CSCF node of Embodiment B2, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to determine whether or not to initiate the use of the additionalsecond user plane for the IMS PDU session by being configured to causethe first P-CSCF node to:

determine based at least in part on a media type indicated in thesession information.

Embodiment B4. The first P-CSCF node of any one of Embodiments B1-B3,wherein the processing circuitry is further configured to cause thefirst P-CSCF node to:

subscribe to an access and mobility management function (AMF) to benotified when a location of the UE is outside of a coverage area of thefirst AGW, the subscription request including at least one of geographiccoordinates indicating the coverage area of the first AGW and geographiccoordinates indicating the location of the UE.

Embodiment B5. The first P-CSCF node of Embodiment B4, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to:

as a result of the subscription, receive a notification that thelocation of the UE is outside of the coverage area of the first AGW, thelocation of the UE indicated in geographic coordinates in the receivednotification; and/or

responsive to the received notification, select the additional secondAGW that has a coverage area corresponding to the indicated location ofthe UE and/or identify a second P-CSCF node that controls the secondAGW.

Embodiment B6. The first P-CSCF node of Embodiment B5, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to identify the additional second AGW by being configured to causethe first P-CSCF node to:

use a table indicating a plurality of AGWs, coverage areas associatedwith each of the plurality of AGWs and, for each of the plurality ofAGWs, an identifier of a P-CSCF node controlling the corresponding oneor more AGWs.

Embodiment B7. The first P-CSCF node of any one of Embodiments B5 andB6, wherein the processing circuitry is further configured to cause thefirst P-CSCF node to:

communicate with the second P-CSCF node, via a P-CSCF-to-P-CSCFinterface, to initiate a context transfer to the second P-CSCF node.

Embodiment B8. The first P-CSCF node of Embodiment B7, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to communicate with the second P-CSCF node, via a P-CSCF-to-P-CSCFinterface, by being configured to cause the first P-CSCF node to one ormore of:

request that the second P-CSCF node reserve at least one InternetProtocol (IP) address in the second AGW for the second user plane andthe local AS;

provide, to the second P-CSCF node, addresses associated with the seconduser plane and the local AS to allow the second P-CSCF node to set-upthe second AGW for the second user plane and the local AS for the IMSPDU session for the UE;

receive, from the second P-CSCF node, the addresses reserved in thesecond AGW for the second user plane and the local AS to use; and/orsubscribe to the AMF to be notified when the location of the UE isoutside of a coverage area of the second AGW.

Embodiment C1. A method implemented in an access and mobility management(AMF) node, the method comprising:

receiving a subscription request, from a P-CSCF node, to be notifiedwhen a location of a user equipment (UE) associated with an IMS PDUsession is outside of a coverage area of a first access gateway (AGW),the subscription request including at least one of geographiccoordinates indicating the coverage area of the first AGW and geographiccoordinates indicating the location of the UE.

Embodiment C2. The method of Embodiment C1, further comprising:

monitoring the location of the UE relative to the coverage area of thefirst AGW; and

if the location of the UE moves outside of the coverage area of thefirst AGW, notifying the P-CSCF node that the location of the UE isoutside of the coverage area of the first AGW, the location of the UEindicated in geographic coordinates in the notification.

Embodiment D1. An access and mobility management (AMF) node, the AMFnode comprising processing circuitry, the processing circuitryconfigured to cause the AMF node to:

receive a subscription request, from a P-CSCF node, to be notified whena location of a user equipment (UE) associated with an IMS PDU sessionis outside of a coverage area of a first access gateway (AGW), thesubscription request including at least one of geographic coordinatesindicating the coverage area of the first AGW and geographic coordinatesindicating the location of the UE.

Embodiment D2. The AMF node of Embodiment D1, wherein the processingcircuitry is further configured to cause the AMF node:

monitor the location of the UE relative to the coverage area of thefirst AGW;

and if the location of the UE moves outside of the coverage area of thefirst AGW, notify the P-CSCF node that the location of the UE is outsideof the coverage area of the first AGW, the location of the UE indicatedin geographic coordinates in the notification.

Embodiment E1. A method implemented in a first proxy-call sessioncontrol function (P-CSCF) node, the method comprising one or more of:

receiving a request from a second P-CSCF node to reserve at least oneInternet Protocol (IP) address in an access gateway (AGW) controlled bythe first P-CSCF node for a user plane and a local application server(AS) associated with an IMS PDU session for a user equipment (UE);and/or

sending, to the second P-CSCF node, the at least one IP address reservedin the second AGW for the user plane and the local AS to use.

Embodiment E2. The method of Embodiment E1, wherein one or more of:

the receiving and sending is via a P-CSCF-to-P-CSCF interface; and

receiving includes receiving, from the second P-CSCF node, addressesassociated with the user plane and the local AS to allow the firstP-CSCF node to set-up the AGW for the user plane for the IMS PDU sessionfor the UE.

Embodiment E3. The method of any one of Embodiments E1 and E2, furthercomprising:

reserving the requested addresses in the AGW for the user plane and thelocal AS to use.

Embodiment F1. A first proxy-call session control function (P-CSCF)node, the first P-CSCF node comprising processing circuitry, theprocessing circuitry configured to cause the first P-CSCF node to one ormore of:

receive a request from a second P-CSCF node to reserve at least oneInternet Protocol (IP) address in an access gateway (AGW) controlled bythe first P-CSCF node for a user plane and a local application server(AS) associated with an IMS PDU session for a user equipment (UE);and/or

send, to the second P-CSCF node, the at least one IP address reserved inthe second AGW for the user plane and the local AS to use.

Embodiment F2. The first P-CSCF node of Embodiment F1, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to one or more of:

receive and send via a P-CSCF-to-P-CSCF interface; and

receive, from the second P-CSCF node, addresses associated with the userplane and the local AS to allow the first P-CSCF node to set-up the AGWfor the user plane for the IMS PDU session for the UE.

Embodiment F3. The first P-CSCF node of any one of Embodiments F1 andF2, wherein the processing circuitry is further configured to cause thefirst P-CSCF node to:

reserve the requested addresses in the AGW for the user plane and thelocal AS to use.

As will be appreciated by one of skill in the art, the conceptsdescribed herein may be embodied as a method, data processing system,and/or computer program product. Accordingly, the concepts describedherein may take the form of an entirely hardware embodiment, an entirelysoftware embodiment or an embodiment combining software and hardwareaspects all generally referred to herein as a “circuit” or “module.”Furthermore, the disclosure may take the form of a computer programproduct on a tangible computer usable storage medium having computerprogram code embodied in the medium that can be executed by a computer.Any suitable tangible computer readable medium may be utilized includinghard disks, CD-ROMs, electronic storage devices, optical storagedevices, or magnetic storage devices.

Some embodiments are described herein with reference to flowchartillustrations and/or block diagrams of methods, systems and computerprogram products. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable memory or storage medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer readablememory produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks. It is to beunderstood that the functions/acts noted in the blocks may occur out ofthe order noted in the operational illustrations. For example, twoblocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality/acts involved. Although some ofthe diagrams include arrows on communication paths to show a primarydirection of communication, it is to be understood that communicationmay occur in the opposite direction to the depicted arrows.

Computer program code for carrying out operations of the conceptsdescribed herein may be written in an object oriented programminglanguage such as Java® or C++. However, the computer program code forcarrying out operations of the disclosure may also be written inconventional procedural programming languages, such as the “C”programming language. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer. In the latter scenario, theremote computer may be connected to the user's computer through a localarea network (LAN) or a wide area network (WAN), or the connection maybe made to an external computer (for example, through the Internet usingan Internet Service Provider).

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, all embodiments can be combined in any way and/orcombination, and the present specification, including the drawings,shall be construed to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

It will be appreciated by persons skilled in the art that theembodiments described herein are not limited to what has beenparticularly shown and described herein above. In addition, unlessmention was made above to the contrary, it should be noted that all ofthe accompanying drawings are not to scale. A variety of modificationsand variations are possible in light of the above teachings withoutdeparting from the scope of the following claims.

1. A method implemented in a first proxy-call session control functionnode, the method comprising: receiving, via a first user planeassociated to an Internet Protocol Multimedia Subsystem (IMS) ProtocolData Unit, PDU, session for a user equipment, UE, a session initiationprotocol (SIP) INVITE message; and as a result of the SIP INVITE messageand based on a location of the UE relative to a first access gateway(AGW), associated to the first P-CSCF node, determining whether or notto initiate use of at least one of an additional second user plane andan additional second AGW for the IMS PDU session for the UE, the atleast one of the second user plane and the second AGW being closer tothe UE than the first user plane.
 2. The method of claim 1, whereindetermining whether or not to initiate the use of the at least one ofthe additional second user plane and the additional second AGW for theIMS PDU session further comprises: determining, based on sessioninformation of the IMS PDU session, whether or not to initiate use of alocal application server, AS, for the IMS PDU session for the UE, and/ordetermining based at least in part on a media type indicated in thesession information.
 3. (canceled)
 4. The method of claim 1, furthercomprising: subscribing to an access and mobility management function(AMF), to be notified when a location of the UE is outside of a coveragearea of the first AGW, the subscribing including at least one ofgeographic coordinates indicating the coverage area of the first AGW andgeographic coordinates indicating the location of the UE, and/or as aresult of the subscribing, receiving a notification that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the received notification;and responsive to the received notification, selecting the additionalsecond AGW that has a coverage area corresponding to the indicatedlocation of the UE and/or identifying a second P-CSCF node that controlsthe second AGW.
 5. (canceled)
 6. The method of claim 4, whereinidentifying the additional second AGW further comprises: using a tableindicating a plurality of AGWs, coverage areas associated with each ofthe plurality of AGWs and, for each of the plurality of AGWs, anidentifier of a P-CSCF node controlling the corresponding one or moreAGWs.
 7. The method of claim 4, further comprising: communicating withthe second P-CSCF node, via a P-CSCF-to-P-CSCF interface, to initiate acontext transfer to the second P-CSCF node; and/or wherein communicatingwith the second P-CSCF node, via a P-CSCF-to-P-CSCF interface, furthercomprises at least one of: requesting that the second P-CSCF nodereserve at least one Internet Protocol (IP) address in the second AGWfor the second user plane and the local AS; providing, to the secondP-CSCF node, addresses associated with the second user plane and thelocal AS to allow the second P-CSCF node to set-up the second AGW forthe second user plane and the local AS for the IMS PDU session for theUE; receiving, from the second P-CSCF node, the addresses reserved inthe second AGW for the second user plane and the local AS to use; andsubscribing to the AMF to be notified when the location of the UE isoutside of a coverage area of the second AGW.
 8. (canceled)
 9. A firstproxy-call session control function (P-CSCF node, the first P-CSCF nodecomprising processing circuitry, the processing circuitry configured tocause the first P-CSCF node to: receive, via a first user planeassociated to an IMS PDU session for a user equipment (UE) a sessioninitiation protocol (SIP) INVITE message; and as a result of the SIPINVITE message and based on a location of the UE relative to a firstaccess gateway (AGW), associated to the first P-CSCF node, determinewhether or not to initiate use of at least one of an additional seconduser plane and an additional second AGW for the IMS PDU session for theUE, the at least one of the second user plane and the second AGW beingcloser to the UE than the first user plane.
 10. The first P-CSCF node ofclaim 9, wherein the processing circuitry is further configured to causethe first P-CSCF node to determine whether or not to initiate the use ofthe at least one of the additional second user plane and the additionalsecond AGW for the IMS PDU session by being configured to cause thefirst P-CSCF node to: determine, based on session information of the IMSPDU session, whether or not to initiate use of a local applicationserver, AS, for the IMS PDU session for the UE; and/or determine basedat least in part on a media type indicated in the session information.11. (canceled)
 12. The first P-CSCF node of claim 9, wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to: subscribe to an access and mobility management function (AMF)to be notified when a location of the UE is outside of a coverage areaof the first AGW, the subscription request including at least one ofgeographic coordinates indicating the coverage area of the first AGW andgeographic coordinates indicating the location of the UE; and/or as aresult of the subscription, receive a notification that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the received notification;and responsive to the received notification, select the additionalsecond AGW that has a coverage area corresponding to the indicatedlocation of the UE and/or identify a second P-CSCF node that controlsthe second AGW.
 13. (canceled)
 14. The first P-CSCF node of claim 12,wherein the processing circuitry is further configured to cause thefirst P-CSCF node to identify the additional second AGW by beingconfigured to cause the first P-CSCF node to: use a table indicating aplurality of AGWs, coverage areas associated with each of the pluralityof AGWs and, for each of the plurality of AGWs, an identifier of aP-CSCF node controlling the corresponding one or more AGWs.
 15. Thefirst P-CSCF node of claim 14, wherein the processing circuitry isfurther configured to cause the first P-CSCF node to: communicate withthe second P-CSCF node, via a P-CSCF-to-P-CSCF interface, to initiate acontext transfer to the second P-CSCF node; and/or wherein theprocessing circuitry is further configured to cause the first P-CSCFnode to communicate with the second P-CSCF node, via a P-CSCF-to-P-CSCFinterface, by being configured to cause the first P-CSCF node to atleast one of: request that the second P-CSCF node reserve at least oneInternet Protocol, IP, address in the second AGW for the second userplane and the local AS; provide, to the second P-CSCF node, addressesassociated with the second user plane and the local AS to allow thesecond P-CSCF node to set-up the second AGW for the second user planeand the local AS for the IMS PDU session for the UE; receive, from thesecond P-CSCF node, the addresses reserved in the second AGW for thesecond user plane and the local AS to use; and subscribe to the AMF tobe notified when the location of the UE is outside of a coverage area ofthe second AGW.
 16. (canceled)
 17. A method implemented in an access andmobility management (AMF) node, the method comprising: receiving asubscription request, from a P-CSCF node, to be notified when a locationof a user equipment (UE), associated with an IMS PDU session is outsideof a coverage area of a first access gateway (AGW), the subscriptionrequest including at least one of geographic coordinates indicating thecoverage area of the first AGW and geographic coordinates indicating thelocation of the UE.
 18. The method of claim 17, further comprising:monitoring the location of the UE relative to the coverage area of thefirst AGW; and if the location of the UE moves outside of the coveragearea of the first AGW, notifying the P-CSCF node that the location ofthe UE is outside of the coverage area of the first AGW, the location ofthe UE indicated in geographic coordinates in the notification.
 19. Anaccess and mobility management (AMF) node, the AMF node comprisingprocessing circuitry, the processing circuitry configured to cause theAMF node to: receive a subscription request, from a P-CSCF node, to benotified when a location of a user equipment, UE, associated with an IMSPDU session is outside of a coverage area of a first access gateway,AGW, the subscription request including at least one of geographiccoordinates indicating the coverage area of the first AGW and geographiccoordinates indicating the location of the UE.
 20. The AMF node (12) ofclaim 19, wherein the processing circuitry is further configured tocause the AMF node to: monitor the location of the UE relative to thecoverage area of the first AGW; and if the location of the UE movesoutside of the coverage area of the first AGW, notify the P-CSCF nodethat the location of the UE is outside of the coverage area of the firstAGW, the location of the UE indicated in geographic coordinates in thenotification.
 21. The method of claim 1, wherein the method implementedin a first proxy-call session control function, P-CSCF, node comprising:receiving a request from a second P-CSCF node to reserve at least oneInternet Protocol (IP) address in an access gateway (AGW), controlled bythe first P-CSCF node for a user plane and a local application server(AS) associated with an IMS PDU session for a user equipment (UE); andsending, to the second P-CSCF node, the at least one IP address reservedin the second AGW for the user plane and the local AS to use.
 22. Themethod of claim 21, wherein at least one of: the receiving and sendingis via a P-CSCF-to-P-CSCF interface; and receiving includes receiving,from the second P-CSCF node, addresses associated with the user planeand the local AS to allow the first P-CSCF node to set-up the AGW forthe user plane for the IMS PDU session for the UE.
 23. The method ofclaim 21, further comprising: reserving the requested addresses in theAGW for the user plane and the local AS to use.
 24. The first proxy-callsession control function node of claim 1, wherein the processingcircuitry is further configured to cause the first P-CSCF node to:receive a request from a second P-CSCF node to reserve at least oneInternet Protocol (IP) address in an access gateway, AGW, controlled bythe first P-CSCF node for a user plane and a local application server,AS, associated with an IMS PDU session for a user equipment (UE); andsend, to the second P-CSCF node, the at least one IP address reserved inthe second AGW for the user plane and the local AS to use.
 25. The firstP-CSCF node of claim 24, wherein the processing circuitry is furtherconfigured to cause the first P-CSCF node to at least one of: receiveand send via a P-CSCF-to-P-CSCF interface; and receive, from the secondP-CSCF node, addresses associated with the user plane and the local ASto allow the first P-CSCF node to set-up the AGW for the user plane forthe IMS PDU session for the UE.
 26. The first P-CSCF node of claim 24,wherein the processing circuitry is further configured to cause thefirst P-CSCF node to: reserve the requested addresses in the AGW for theuser plane and the local AS to use.